首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   13377篇
  免费   823篇
  国内免费   118篇
耳鼻咽喉   179篇
儿科学   500篇
妇产科学   424篇
基础医学   1168篇
口腔科学   401篇
临床医学   1249篇
内科学   2761篇
皮肤病学   237篇
神经病学   600篇
特种医学   684篇
外科学   2508篇
综合类   564篇
现状与发展   1篇
一般理论   12篇
预防医学   848篇
眼科学   274篇
药学   1032篇
  2篇
中国医学   107篇
肿瘤学   767篇
  2023年   127篇
  2022年   375篇
  2021年   569篇
  2020年   332篇
  2019年   389篇
  2018年   494篇
  2017年   298篇
  2016年   393篇
  2015年   415篇
  2014年   551篇
  2013年   726篇
  2012年   973篇
  2011年   940篇
  2010年   574篇
  2009年   480篇
  2008年   676篇
  2007年   744篇
  2006年   700篇
  2005年   592篇
  2004年   528篇
  2003年   449篇
  2002年   428篇
  2001年   163篇
  2000年   138篇
  1999年   129篇
  1998年   149篇
  1997年   127篇
  1996年   115篇
  1995年   101篇
  1994年   82篇
  1993年   77篇
  1992年   100篇
  1991年   71篇
  1990年   80篇
  1989年   88篇
  1988年   85篇
  1987年   86篇
  1986年   53篇
  1985年   74篇
  1984年   48篇
  1983年   61篇
  1982年   36篇
  1980年   35篇
  1979年   38篇
  1978年   33篇
  1977年   41篇
  1974年   35篇
  1973年   35篇
  1955年   42篇
  1954年   38篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
High-frequency ultrasound (US) is an efficient, rapid and inexpensive altenative to magnetic resonance imaging (MRI) for investigation of diseases in the soft tissues of the wrist and hand. US allows detection of foreign bodies and the reliable identification of a variety of traumatic lesions affecting tendons, annular pulleys, ligaments, vessels and nerves. Inflammatory diseases of tendons, including acute and chronic tenosynovitis and some degenerative conditions in the wrist and hand, can also be diagnosed. In entrapment neuropathies, US is able to identify nerve shape changes and possible extrinsic space-occupying lesions that may cause nerve compression within the tunnels. In patients with localized swelling of the hand or wrist, US is able to assess the presence of an expansile lesion and to characterize its nature in most cases. The objective of this article is to review the main findings and the primary indications of US in the investigation of disorders of the hand and wrist. Received: 10 September 1998 Accepted: 24 November 1998  相似文献   
102.
103.
The prevalence of antibodies against spotted fever group rickettsia (SFGR), murine typhus and Q fever were investigated in wild rats captured in Indonesia. Sera of 327 rats were collected from Jakarta and Boyolali on Java Island. The prevalences of antibodies against SFGR and murine typhus were 128 (39.1%) and 48 (14.7%), respectively. Antibodies against Q fever were not detected in these serum samples. Antibodies against SFGR were found in all species of rats (20.8–51.9%). The antibody positive rate against murine typhus in Rattus norvegicus (38.0%) was significantly higher than that in other rat species (0–4.8%, p < 0.01). The antibody positive rates against SFGR and murine typhus in rats captured in Jakarta were significantly higher than those in rats captured in Boyolali (p < 0.01). In this survey, all species of rats had antibodies against SFGR, indicating that the 4 species of tested rats (R. norvegicus, R. rattus, R. exulans, R. tiomanicus) were infected with SFGR and that SFGR may infest the whole of Java Island. Most of the rats that were antibody-positive against murine typhus were captured in Jakarta. Therefore, R. norvegicus and R. rattus are likely to be important hosts of murine typhus in Jakarta. The antibody-positive rates against SFGR and murine typhus in rats captured in the dry season were significantly higher than those in rats captured in the rainy season. This may coincide with the active periods of ticks and fleas in Indonesia.  相似文献   
104.
105.
The ability of some N,N-dialkylaminosubstituted chromones and isoxazoles to inhibit the protein kinase C (PKC) dependent signal transduction pathway was tested. As a cellular model, human neutrophils stimulated with either phorbol myristate acetate (PMA) or formylmethionine-leucine-phenylalanine (f-MLF) were used. The efficiency of the compounds was established by their capacity to reduce the O2- production by activated human neutrophils. Compounds carrying a 3-bis(2-methoxyethyl)amino group, a substituent found active in previously tested tricyclic compounds, do not show significant anti-PKC activity in this study. On the other hand, substitution with a 1-piperidinyl group leads all tested compounds to a high biological activity against stimulated neutrophils.  相似文献   
106.
This study was carried out to determine the risk of some social and biological maternal factors which may contribute to occurrence of anemia among mothers and preschool children. A community based comparative study was chosen for the conduction of this work. The target population were 400 women in the child bearing period, having at least one preschool child (440). Capillary blood samples were taken by finger prick method and hemoglobin level was estimated by Sahly method. According to the cut off level of hemoglobin, women were classified into anemic and non anemic. In addition to that, 440 preschool children belonging to these women were classified according to the cut off level of their hemoglobin into 165 anemic children and 275 non anemic ones. An interview questionnaire was used to collect the data. Analysis of results showed that age of mother (30 years and above), illiteracy, high parity, history of previous abortion, history of previous perinatal mortality, small inter-birth interval and non use of contraceptives are significant risk factors for mothers. However, mother occupation and state of pregnancy has no role in occurrence of anemia among mothers. In addition to that, high parity, history of previous abortion, history of perinatal mortality, short inter-birth interval, non use of contraceptives and pregnancy are maternal risk factors responsible for anemia among preschool children. While, mother age, education and occupation has no role for occurrence of anemia among preschool children.  相似文献   
107.
108.
Possible effects on the next generation after long-term exposure (subcutaneous administration) of male rats to very high doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) were studied. Two dose regimes were applied: TCDD-25 (initial dose: 25 g/kg body wt; maintenance dose: 5 g/kg body wt, once weekly) and TCDD-75 (initial dose: 75 g/kg body wt; maintenance dose: 15 g/kg body wt). Male rats were treated for 10 weeks before mating and then throughout the entire 12 week mating period. They were mated to unexposed virgin females. One group of pregnant females was used for teratological evaluations, and another group was allowed to deliver. No significant differences were observed in the number of implantations or fetuses per litter, and resorption rate, and fetal weight between the controls and TCDD-treated groups. No gross-structural anomalies occurred in any of the fetuses sired by TCDD-treated males. In the TCDD-25 group an increased frequency of two types of variations was observed which also occur in controls: incompletely ossified fingers (TCDD-25=5.1%, controls=2.6%), and incompletely ossified ossa zygomatica (TCDD-25=1.8%, controls=0.5%). In the TCDD-25 group a slight but statistically significant increase was observed in the rate of stillbirths (TCDD-25=1.3%, controls=0.1%), apparently due to an unusually low frequency occurring in the controls (overall historical controls=0.6%). There was no difference in postnatal mortality (TCDD-25=1.3%, controls=1.3%). Taken together, despite the very high doses of TCDD used, the data do not provide evidence for biologically significant paternally-mediated developmental toxicity in the fetuses and newborn.  相似文献   
109.
The effects of a single dose of TCDD on the testis were studied in rats. The animals were treated (subcutaneously) once with TCDD doses of 0, 0.5, 1.0, 3.0, 5.0 g/kg body weight. Doses of 3.0 or 5.0 g TCDD/kg reduced the number of spermatids/testis significantly (60% of the controls). Electron microscopic inspection revealed that both doses led to a dissolution on the germinal epithelium. Altered germ cells at all developmental stages occurred in all testes evaluated. Doses of 0.5 or 1.0 g TCDD/kg did not induce any effects in the testis; therefore, under these experimental conditions of single exposure to rats the dose of 1.0 g TCDD/kg can be considered as NOAEL.  相似文献   
110.
From November 1979 through December 1989, 210 distal arteriovenous fistulas were constructed as adjuncts to tibial and peroneal vascular reconstructive procedures in 203 patients threatened with limb loss. Two-year cumulative patency rates were calculated by grouping patients on the basis of changing indications in sequential time periods: group 1 (n = 61): 1979 to 1983, 18%; group 2 (n = 80): 1983 to 1986, 33%; group 3 (n = 69): 1986 to 1989, 44%. Although the therapeutic results observed in these groups are not statistically comparable, they show a perceptible trend. Postoperative arteriography showed that flow is prograde in the distal vessels beyond the distal arteriovenous fistula. Graft surveillance by duplex ultrasonography also confirmed that flow in the distal arteries is prograde and that "steal" does not occur. Peak systolic velocity (174 +/- 38 cm/sec) and mean velocity (92 +/- 23) flow rates are increased in grafts with patent distal arteriovenous fistulas compared to those bypasses with closed distal arteriovenous fistulas (p less than 0.01). There were no differences in the flow measurements for the arteries beyond the distal anastomoses and distal arteriovenous fistulas, confirming the prograde nature of the distal flow. In 22 patients analysis of graft and fistula patency by duplex sonography showed that one fourth of all grafts were patent without fistulas at 1 and 2 years after operation. Alternatively, 68% of patent grafts at 1 year had patent fistulas and 58% had patent fistulas at 2 years. We conclude that the distal arteriovenous fistula will increase graft flow and simultaneously prevent distal arterial overload without causing "steal." This technique should be considered whenever a prosthetic graft is necessary for crural reconstruction and only in selected instances of revascularization with autologous veins.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号